Simplify the Expression $( \sqrt { 7 } + \sqrt { 6 } ) ( \sqrt { 7 } - \sqrt { 6 } )$

Multiple Choice

Simplify the expression. Assume all variables represent positive real numbers.
- $( \sqrt { 7 } + \sqrt { 6 } ) ( \sqrt { 7 } - \sqrt { 6 } )$

A) $7 + 2 \sqrt { 42 }$
B) $7 - 2 \sqrt { 42 }$
C) 13
D) 1